1. Field of the Invention
The present invention relates to a bar code reader and, more particularly, to a bar code reader used for a POS (point-of-sale) system which is installed on a counter of a store and is used for reading bar codes attached to goods.
2. Description of the Related Art
In POS systems and in physical distribution systems, so far, it has been a widely accepted practice to exactly calculate and manage goods by reading bar codes. The bar codes are attached to the goods and are read by using a bar code reader.
In such a bar code reader, a ray of light such as laser light is emitted onto the bar code, which is attached to the article by printing or the like method. Thus the bar code reader scans the bar code surface, and the laser light reflected by the bar code is detected to read the bar code.
FIG. 1A is a diagram illustrating a conventional bar code reader in a perspective manner so that the internal structure can be seen. The bar code reader employs a source of laser light, such as a semiconductor laser, as a source of light. In FIG. 1A, reference numeral 201 denotes a laser module constituted by a laser beam source and lenses. Reference numeral 202 is a polygon mirror, which is a polyhedral mirror having a plurality of reflection planes. The polygon mirror 202 is rotated by a motor 207. The laser beam emitted from the laser module 201 is reflected by a small plane mirror provided at the center of a concave mirror 203 and arrives at the reflection plane of the polygon mirror 202. The laser beam is reflected by the reflection plane of the polygon mirror 202. Here, however, since the polygon mirror 202 is rotating, the laser beam is scanned, for example, in the clockwise direction in the drawing.
Reference numeral 204 denotes mirrors for splitting the scanning line and on which is incident the laser beam scanned by the polygon mirror 202. The laser beam is downwardly reflected by the scanning line-splitting mirrors 204, upwardly reflected by a bottom mirror 205 of nearly a V-shape, and is emitted through a reading window 206.
The laser beam emitted from the reading window 206 scans the article that passes over the bar code reader. The laser beam, after having scanned the article, is reflected by the surface of the article to which the bar code is attached, and is caused to be incident on the bar code reader through the reading window 206.
Light reflected by the bar code of the article and incident on the bar code reader, is reflected by the bottom mirror 205, scanning line-splitting mirrors 204 and polygon mirror 202, and is caused to be incident on the concave mirror 203. The concave mirror 203 focuses the laser beam reflected and diffused by the bar code toward a light detector 208. The laser beam received by the light detector 208 is decoded by a decoding circuit in the bar code reader and is output to an external unit.
The bar code reader shown in FIG. 1A has only one reading window 206. Such a bar code reader can be installed on an accounting counter in a store in two ways. I.e., the bar code reader is installed so that the reading window 206 is in flush with the surface of the accounting counter, or the bar code reader is so installed that the reading window 206 is nearly vertical to the surface of the accounting counter.
When the bar code reader of FIG. 1A is installed on the accounting counter, there is offered only one reading window 206 as described above. When the article is passed over the bar code reader at the accounting counter to read the bar code attached to the article, the bar code is not scanned by the scanning light unless the bar code faces the reading window 206, and the bar code is otherwise not read out. This is because in conventional bar code readers, a limitation is imposed on the range scanned by the scanning light or on the direction in which the scanning light is emitted.
To solve the above problem, a bar code reader has in recent years been devised having a plurality of reading windows. Such a bar code reader emits the scanning light through the respective reading windows to scan the article having bar code from a plurality of different directions.
FIGS. 1B and 1D illustrate appearances of bar code readers 210 and 220 in which the above-mentioned countermeasure is taken. These bar code readers 210 and 220 are provided with reading windows (hereinafter referred to as bottom windows) 216, 226 formed in the bottom surface of the device, and reading windows (hereinafter referred to as side windows) 217, 227 formed in the side surface erected at an angle nearly vertical to the bottom windows 216, 226. Scanning light is emitted from the bottom windows 216, 226 toward the upper side windows 217, 227. On the other hand, scanning light is emitted in nearly the horizontal direction (toward the operator) from the side windows 217, 227.
As shown in FIGS. 1C and 1E, the difference between the bar code readers 210 and 220 is that the bottom window 216 of the bar code reader 210 has a size of 5 inchesxc3x974 inches, whereas the bottom window 226 of the bar code reader 220 is of a trapezoidal shape having a size of 6 inchesxc3x976 inches.
As described above, a plurality of reading windows are provided, and the scanning light is emitted in a plurality of directions through the respective reading windows. Therefore, the article 209 passing on the bar code readers 210, 220 is irradiated with scanning light from a plurality of directions, and the probability for scanning the bar code is enhanced compared with when a bar code reader having only one reading window is used.
FIG. 1F illustrates a calculation counter (check-out counter) 230 on which the above-mentioned bar code reader 220 is installed. On the check-out counter 230 is installed the bar code reader 220. The operator P stands at a position facing the side window 227.
On the upper side of the side window 227 is provided a key board 222 for inputting data related to the goods to which no bar code has been attached. A belt conveyer 233 exists on the upstream side of the check-out counter 230 to carry the goods to the position of the bar code reader 220. Reference numeral 235 denotes a guide plate for guiding the goods onto the bottom window 226 of the bar code reader 220.
As the article is carried to the position of the bar code reader 220 and passes by the bar code reader 220, the bar code is read out irrespective of the direction of the bar code attached to the article. A POS terminal 234 is provided by the side of the operator P, and the calculation processing is executed by the POS terminal 234.
FIG. 1G illustrates a bar code readable area of the bar code readers 210 and 220 of FIGS. 1B and 1D. Here, the hatched region RP represents the region where the scanning beams emitted from the side windows 217, 227 and the bottom windows 216, 226 are focused. In this region bar code is read out even when the bar code is turned in the horizontal direction by 360 degrees. Thus, since the scanning beams are emitted from the two reading windows, the bar code readable area is broadened. Besides, even when the bar code surface does not completely face one reading window, the bar code can be read out.
However, even such bar code readers have problems as described below. In the case of the bar code reader 210 shown in FIGS. 1B and 1C, for example, the bottom window 216 has a size of 4 inchesxc3x975 inches. Thus, the bar code reader 210 shown in FIGS. 1B and 1C has a narrow bottom window 216, and a pattern (hereinafter referred to as scanning pattern) is constituted by a small number of scanning lines emitted from the bottom window 216.
In the case of the bar code reader 220 shown in FIGS. 1D and 1E, furthermore, the bottom window 226 has a size of 6 inchesxc3x976 inches, which is larger than the size of the bottom window 216 of the bar code reader 210 shown in FIGS. 1B and 1C. However, the bottom windows 216, 226 are usually constituted by a reinforced glass which resists falling articles, and are, hence, expensive. Therefore, the bar code reader 220 of FIGS. 1D and 1E becomes expensive.
Various optical systems are arranged in a bar code reader, and the arrangement must be so contrived that the reader does not become bulky. However, in the conventional bar code readers and, particularly, in the bar code readers 210, 220 which read the bar code through two surfaces (i.e., through the bottom windows 216, 226 and the side windows 217, 227), a total of two laser beam sources are provided: a laser beam source for the bottom windows 216, 226 and another laser beam source for the side windows 217, 227. Therefore, arrangement of the optical systems for accomplishing a desirable reading ability involves various limitations and problems, resulting in an increase in the size of the device and an increase in the cost of production.
The object of the present invention is to provide a bar codes reader for reading bar code using a bottom window and a side window, wherein only one source of light is employed to emit laser beam from the bottom window or the side window. The arrangement of the optical systems in the bar code reader is so contrived that the device will not bulky, and the device is fabricated at a reduced cost. Another object of the present invention is to read the bar code attached to an article maintaining an improved precision by increasing the number of scanning patterns emitted from the bottom window.
According to the present invention, in particular, it is possible to increase the number of scanning lines for constituting a scanning pattern emitted from the bottom window compared with that of the conventional devices. This is accomplished by the arrangement of mirrors for forming scanning patterns.
According to the present invention, furthermore, the external size of the device and, particularly, the depth can be decreased compared with the conventional devices. This makes it possible to install the reader even on a narrow accounting counter.
In the present invention, a source of light, scanning means, focusing means and the like constituting an optical system are arranged on the center line of the device so as to share the same optical axis. In particular, the ray of light guided by the reflector is caused to intersect the axis of rotation of the scanning means. Therefore, no extra space needs be formed in the reader for conducting the ray of light, and the device can be realized in a small size. Moreover, the ray of light conducted by the reflection mirror is allowed to pass under the scanning means, making it possible to decrease the height of the device.
The light detector is so disposed on the bottom surface of a bottom scanner portion that the light-receiving surface is faced in the horizontal direction and is so disposed in the side scanner portion that the light-receiving surface is faced downwards, in order to effectively utilize space in the device. In this case, the light detector does not intercept the passage of rays light such as scanning lines. Accordingly, limitation on the length of the scanning lines, on the direction and on the angle can be decreased to realize a scanning pattern for reading the bar code more efficiently.
In the present invention, furthermore, the frame of the bottom scanner unit is divided into upper and lower portions, and the mirrors for forming the scanning patterns are mounted on the inside of the frame. Therefore, no additional mechanism is necessary for arranging the mirrors in space inside the device; i.e., space in the device is effectively utilized.
Moreover, since the depth of the bottom window is increased compared with the conventional bar code readers, the area for reading bar codes can be broadened compared with that of the conventional devices, and it becomes more probable that the bar code can be read compared to the conventional devices.
To focus light reflected by the bar code and guided to the detector, furthermore, the optical passage of the reflected beam is folded by using a concave mirror, making it possible to shorten the length of the passage of the reflected beam.
According to the present invention, furthermore, the beam diameter of a semiconductor laser of either the vertical direction or the horizontal direction is changed by using a rectangular prism, but the other beam diameter is not changed; i.e., the beam diameters are set to be nearly the same in both the horizontal direction and the vertical direction. According to this constitution, the laser beam is less intercepted (squeezed) by, for example, an aperture, and the diameter of the laser beam is not deformed.
In particular, use of the rectangular prism makes it possible to reduce the size of the laser module.
With the source of laser beam, means for changing the beam diameter and means for splitting the beam being contained in a module, furthermore, there is no need to bring the optical axes of each of the portions into alignment.